Life rafts must be able to be towed by means of towing lines. To this end, life rafts are equipped with a member, such as a ring or the like, appropriate for attaching the end of the towing line. This ring is usually fixed to the wall of the float via a loop made of a flexible material which in turn is fixed (e.g. by adhesive bonding or welding) to the float wall.
An arrangement of the above type is in principle relatively reliable and sufficient to withstand typically a tractive force of around 500 kgf which was formerly required for rafts intended for pleasure craft.
However, the problem with such an arrangement is that the entirety of the tractive force is applied to the wall of the float in a very localized manner at one or two points and its reliability depends entirely on the mechanical strength of the fixings and of the wall. In practice, there have been incidents in which the attachment of the towing line has failed due to detachment of the ring retention loop or local tearing of the float wall.
It is also prior art to attach the towing line to a lashing hung garland-fashioned around the periphery of the float. The problem with this approach is that the lashing is engaged loosely through loops and is not rigidly fixed to the float itself. The tensile force applied to the lashing is thus transferred to the float in an irregular way at local points of the float (loops, fixings of the ends of the lashing), and there is still a risk of failure or tearing under heavy loads. Furthermore, if the lashing fails the towing option is lost.
New standards now require not only that rafts be able to withstand even greater towing forces (approximately 800 to 1000 kgf for pleasure rafts) but also that towing be unaffected by lashing failure. Currently known life raft arrangements fail to meet these new requirements in any certain and reliable way.